Horse Sense: "Modular" in the popular term "mod motor" refers to one of Ford Motor Company's operation protocols. At the company's engine plants (Windsor and Romeo), "modular" stands for manufacturer's tooling that can be quickly changed out to facilitate efficient production of 4.6, 5.4, and other engines.

When you're as deeply engrossed in the Mustang hobby as we are, conjuring up different "wouldn't it be cool if..." ideas probably happens in the same rapid-fire succession as ours-or at least Editor Turner's. We really dig the fact that our tech spectrum ranges anywhere from "wham-bam" upgrades to projects that push the envelope of near-impossibility for '79-'08 Mustangs. We hope that you, our readers, enjoy learning about 'Stangs as much as we do.

Engine swaps are the focus of this report. We'll be talking about tried-and-true conversions such as the 5.0-to-351W or 460 big-block-arguably one of the first few engine-exchange procedures ever performed on Fox Mustangs-and other more radical powerplant trades.

Many of today's popular engine exchanges involve installing post-'95 modular engines of all types under the hoods of 'Stangs that we now categorize as being early ('79-'93 Fox) models, as well as newer Mustangs (SN-95s to present).

While a cool swap is usually done to add a performance punch to a 'Stang, it's the sight of an against-the-grain bullet sitting between the fenders in "How did they even get it in there?" glory that makes our heart rate jump.

We'd love to be able to provide step-by-step, how-to instructions on the engine swaps mentioned in this story, but there isn't enough room to do so. The purpose of this guide is to let you know about the parts, principles, and some of the critical procedures that comprise a successful change from one engine to another.

Some of you might be thinking, Engine out, engine in-what's so difficult about that? The truth of the matter is there's a lot more involved nowadays than just making a simple replacement. Engines and Mustangs have changed a lot throughout the years. Today's swaps must be approached from more of an analytical perspective than they were in years past-especially when attempting an endeavor that's more over the top than throwing a 5.0 in a former four-banger Fox.

The process is no longer about the nuts, bolts, and hard parts alone. Computers, wiring, and tuning play a major role in most popular swaps of the new era, and there are many other parts and procedures that have equally high levels of importance. Cost of parts and labor is also a major point of concern. While some engine swaps can be done cheap, those that involve a lot of fabrication, reconfiguring the car, and time on the dyno getting the tune right, can end up being pricey when all is said and done.

In our research for this report, we tapped into the ongoing discussions in the 4.6/5.4 forums of several popular Mustang enthusiasts' Web sites (www.streetstangs.net, www.hardcore50.com, www.modularfords.com, and www.modularfox.com, among others) and found that a wealth of good information on various flavors of modular swaps is a few mouse clicks away.

Understand that we're going just below the surface of a topic that is huge. We realize there are nuances, tricks, and things to note for any type of engine swap that may not be mentioned in this report. Remember, you're doing something that the factory didn't and doesn't have in its plans for these 'Stangs, so there will be bumps in the road. The sense of accomplishment after a successful swap is a great reward for your hard work.

There are a lot of pluses in taking a 'Stang to the next level with a different engine, as you'll see in the collection of notes we've assembled and the awesome examples of completed engine-swap projects that are featured in this issue.

Fox 'Stang enthusiasts have looked to the 351W for years as an easy way to increase power and torque through an engine change. This in-progress Windsor swap we found at Extreme Automotive features a 76mm turbocharger and ACCEL DFI engine management system. Note the width of the intake manifold, as it differs from a 5.0's. Tubular K-members are recommended but aren't necessary, but understand there may be oil-pan or K-member clearance issues if you choose to use drop-engine mounts. While factory steering gear (rack-and-pinion) is reusable, installing a Flaming River steering shaft is the best bet for alleviating any clearance problems with headers.

SN-95 and New Edge fans have unofficially appointed Ford's 4.6 DOHC '03-'04 Cobra engine as one of the most popular swap engines for '94-'04 non-Cobra 'Stangs. This Terminator bullet, topped with a Kenne Bell 2.2 supercharger, awaits entry into a '98 convertible GT at B&D Racing. Mase Rowland tells us there's a significant amount of wiring that must be reconfigured, for accessories such as a relocated alternator, among others. We also hear that B&D is working with a company on a new wiring harness that will adapt a '96-'98 GT's factory DIS electronics to the coil-on-plug ignition system of post-'98 modulars. Enthusiasts who want to keep their cool will also have to install a Cobra's air conditioning lines and condenser or modify the GT's pieces for proper fit and function. A larger or '97-'03 Cobra radiator and '97-'00 electric fan are recommended. A snake's radiator can also be modified to fit and work in a DOHC-implanted Fox Mustang.

Looking right at home is one of the big criteria that separates a good swap from a so-so engine exchange. This Fox plays host to a Four-Valve Cobra engine that's enhanced with Vortech's S-Trim centrifugal supercharger, and if it weren't for the bling that says "it's custom" in any language, you would think this setup was laid in by Ford. Racecraft's mod-motor-in-Fox-Mustang K-member plays a big role in that. In addition to the blower, custom exhaust headers are the standout highlights that give this 'Stang its "cool." Swapping the DOHC mill and adding a power adder requires a return-style fuel system such as Aeromotive's, or that of a '96-'98 'Stang, which might do you better in the bucks department.

As we explained in our cover story on Don Bowles' '06 race 'Stang, you never know what kind of test bullet the crew at Roush Engineering is going to put between its fenders, as the 'Stang is a rolling testament to engine swaps. This experimental mill, which sucks down E85 fuel instead of traditional race gas, packs enough power to send Don down the 1,320 with low-nine-second e.t.'s without a power adder. What's involved with getting this beast into a 'Stang? We're waiting to find out. When we learn the deep secrets of the experimental engine, you'll be the first to know.